Please, help me get my bike back on the road! Crank issues.

Back in February I was clipped by a taxi which took my pedal off my left crank arm and the threads with it.

I then bought a new left crank arm, its important to mention the bike is a early 70's Peugeot roadbike (fixed gear) with cotter pin cranks. I had to have my existing arm cut off as it wouldn't budge.

I went to put the new arm on and found it is 14.8mm rather than 15mm so it won't go on. Even with a good amount of wd40 and a hammer I couldn't get it on. I thought maybe I got a duff crank arm so I acquired two more off forum members and same again, it won't go on!

Its been 6 months since i've had my bike on the road and I desperately need to get it back, tube fares are killing me!

Does anyone have a solution, preferably the cheapest option.
I considered getting a new BB and everything but apparently the threads run in the opposite direction so even that wouldn't be very cheap.

Help would be hugely appreciated guys.

Thanks

Ditch the cottered cranks.

Get a threadless bottom bracket (£15 ish) so you don't have to worry about french/swiss BB threads and then invest in a standard square taper chainset.

Problems all solved.

Agree with ^ re getting a cartridge bottom bracket - cottered stuff is not good to work with.

I've known some people who had trouble keeping the threadless bbs tight, and they ended up creaking a lot. You therefore might wanna think about picking up a threaded one for your thread directions without much trouble (as I have done). Just make sure your axle length is right. Should be around 108mm, but best to check with Sheldon Brown or other lfgss'ers who've had more experience with single speed options (plus it can differ depending on the new cranks you procure).